var argvArr = process.argv;
var str = argvArr[2];

if(str == null || str == '--help' || str == '-h'){
    console.log('没有命令行参数');
}
else if(argvArr.length > 3){
    console.log(eval(argvArr[2]));
}
else if(isNaN(eval(str)) == true){
    console.log("error");
}
else{
    console.log(eval(str));
}
